1. Field of the Invention
The invention relates to improvements in methods and apparatus for the transmission and reception of communications information, and more particularly to an improved method and apparatus for distributing data correction, compression, and decompression functions within transmitting and receiving hardware systems.
2. Technical Background
Requirements for communication between digital computers and computing machines are rapidly increasing, particularly with the increasing popularity of home or personal computers (PCs). Needs for improved communications with higher speeds and error free transmissions are increasing, in part due to increased user sophistication and desires to maximize the cost savings associated with shorter transmissions at higher speeds.
Techniques and algorithms for compressing user information exist today. Such techniques enable increased throughput rates and effective higher speeds. Additionally, techniques, algorithms, or protocols exist for providing error free information, and in fact, industry standards, such as xe2x80x9cMNPxe2x80x9d and xe2x80x9cV.42xe2x80x9d have been adopted in this regard.
Both MNP4 and V.42 provide synchronous error correction capabilities. In accordance with these protocols, information is grouped into packets and encoded with a cyclic redundancy check (CRC). When the packets are received, they are checked to insure that the CRC is correct and then passed to the data terminal equipment (DTE) for processing. If the CRC is found to be incorrect, the received block is discarded and a request is issued for the packet to be resent.
In the communication process, a connection is established between the two communicating nodes before the information packets are passed. This connection is established using an asynchronous data mode typically consisting of 7 or 8 bit information characters, framed by a leading start bit, a trailing stop bit and optional parity bit. During the asynchronous mode, the communicating nodes pass information to negotiate the actual MNP or V.42 correction/compression packet operating mode. Once the packet operating mode is negotiated, the two communicating nodes are switched to a synchronous mode and the information packets are transferred. In the synchronous mode, the information packets are framed by leading multiple 8-bit starting flag characters and trailing multiple 8-bit ending flag characters.
In order to implement these standards, increased processing capabilities and additional ROM and RAM are required. These additional requirements are currently provided in the data communication equipment (DCE). A standard DCE implementation without correction or compression generally contains a modem (modulator/demodulator), possibly a modem controller with memory, and miscellaneous glue logic. To upgrade the DCE to include full V.42 capabilities (MNP4,5, V.42, and V.42 bis) requires that the DCE be provided with an additional 16K-32K ROM and 16K-32K RAM and a controller with a processing bandwidth of 2 mHz. The range of values indicated are all implementation dependent. These additional components and requirements all contribute to an increased DCE system cost.
This increased system cost is not strictly monetary. The extra ROM and RAM as well as an additional controller, or an existing controller with increased operating speed, can easily increase the power dissipation of the design by 400 to 750 milliwatts. The added components can increase the required physical implementation space by as much as 2 to 3 square inches. Moreover, the actual data processing required of the DCE processor essentially precludes the DCE processor from other uses, if the data transmission is to be accomplished within a reasonable time.
Some applications, particularly lap top, notebook, and pocket computer implementations are size and power limited. Consequently, there exists a need for a method and apparatus which minimizes the DCE physical size and design complexity and redistributes processing and power requirements between the DTE and DCE.
In light of the above, it is, therefore, an object of the invention to provide an improved communication system of the type that includes a modem for data transmitting and receiving.
It is another object of the invention to provide an improved communication system of the type described in which the computer portion of the system can be implemented in any communication system having a CPU with sufficient memory and processing bandwidth such as an off-the-shelf personal computer, laptop computer, or the like.
It is another object of the invention to provide an improved modem system that can be used in conjunction with computer systems of the type described above, or the like, that does not require modification of the computer system hardware with which it is used.
It is another object of the invention to provide an improved modem system of the type described in which the hardware requirements of the modem can be greatly reduced.
It is yet another object of the invention to provide a modem system of the type described in which the data error correction and compression processing are not performed in the modem or its associated hardware.
It is yet another object of the invention to provide a modem system in which the cost, power dissipation, and size of the modem are reduced.
It is yet another object of the invention to provide an improved modem system of the type described in which the modem can be simultaneously operated in communication and command modes.
It is yet another object of the invention to provide a new protocol interface and command structure for protocol negotiation and modem configuration control by a host computer.
It is yet another object of the invention to provide an improved communication system that enables data transmission and receiving capabilities using existing industry standards, such as MNP and V.42.
It is yet another object of the invention to provide an improved modem system that is compatible with existing computer located modem control software interfaces.
It is yet another object of the invention to provide an improved modem system that enables a host computer to perform error correction and data compression and transfer data asynchronously to and from the modem, the modem adding and deleting asynchronous framing information from the data and synchronously communicating the data to a remote data communication system.
It is another object of the invention to provide an improved communication system employing a modem for data transmitting and receiving in which the data packetizing is performed by the computer and its associated hardware instead of by the modem and its associated hardware.
These and other objects, features and advantages of the invention will be apparent to those skilled in the art from the following detailed description of the invention, when read in conjunction with the accompanying drawings and appended claims.
In accordance with a broad aspect of the invention, a method and apparatus are provided to allow existing memory and processing resources resident in the DTE to be used for correction and compression processing, thus minimizing the DCE design and eliminating additional system costs, while providing a compatible MNP and V.42 capability with minimal DCE system components and cost.
It is another broad aspect of the invention to provide a communication system that includes a CPU and associated memory for containing instructions for sequential execution by the CPU. A modem is provided separate from the CPU and memory, the modem being operable in a data transmitting and receiving (xe2x80x9ccommunicationxe2x80x9d) mode and in a control mode. The modem is attached via data and control busses to the CPU. Circuitry is also provided in the modem for receiving commands from the CPU for causing the modem to operate simultaneously in both the control and data communication modes. xe2x80x9cCommunicate,xe2x80x9d as used herein, means to transmit data, to receive data, or to do both. The present invention is therefore applicable to transmit-only modems, to receive-only modems, and to modems which have the capability both to transmit and to receive data.
In accordance with yet another broad aspect of the invention, a modem system is presented for use with a host communication system that has a CPU and a memory. The modem system includes a modem connected to accept data and control information from the CPU as well as provide demodulated data and status/monitor information to the CPU. The modem system modulates transmit data provided by the CPU into transmit modem audio and demodulates receive modem audio into receive digital data to be provided to the CPU.
The CPU memory contains a program for execution by the CPU which supports the modem system data and control interfaces as well as data compression/decompression, error correction, and data packetization functions.